The production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon is known in the art. Such a process is typically conducted in the presence of a catalyst composition formed from a compound of a Group VIII metal, particularly a salt of palladium, the anion of a strong non-hydrohalogenic acid and a bidentate ligand, often a bidentate ligand of phosphorus. The polymer products, now known as polyketones or polyketone polymers, are represented by the repeating structure ##STR1## wherein A is the moiety of at least one ethylenically unsaturated hydrocarbon polymerized through the ethylenic unsaturation thereof. It is known from U.S. Pat. No. 4,786,714 and published European Patent Application 259914 to use as the bidentate ligand of the above catalyst compositions a nitrogen-containing ligand. These references employ, inter alia, 2,2'-bipyridine and (2-pyridyl)diphenylphosphine respectively.
When linear alternating polymers of carbon monoxide and ethylene are prepared, the moieties of the polymer which are derived from carbon monoxide are present as carbonyl groups in a high percentage. If, however, the linear alternating polymer is produced from carbon monoxide and propylene, a larger percentage of the carbon monoxide-derived polymer moieties are present as a 3-alkyl-2,5-furandiyl group. Typically, the degree of furanization, i.e., the extent to which carbon monoxide-derived moieties are found as 3-alkyl-2,5-furandiyl groups rather than as carbonyl groups is as high as 10% and in some cases is as high as 50%. The presence of such furandiyl groups is generally undesirable. These groups are detrimental to the stability of the linear alternating polymer and furthermore reduce the possibility for functional modification of the polymer through chemical reaction at the carbonyl groups. It has been found that if an amine is added to a polymerization product mixture during purification of the linear alternating polymer, the degree of furanization of the purified polymer is somewhat lower than if no amine had been added. However, the post-polymerization addition of amine does not reduce the presence of 3-alkyl-2,5-furandiyl moieties to an acceptable level. It would be of advantage to provide an improved process of producing linear alternating polymers of carbon monoxide and propylene wherein a reduced formation of 3-alkyl-2,5-furandiyl moieties in the polymer chain is observed.